Antihistamines are widely accessible medications used to alleviate common allergy symptoms like sneezing, itching, watery eyes, and a runny nose. This article aims to clarify the implications of concurrently taking two common antihistamines, Benadryl and Allegra, which have distinct properties and potential for additive effects.
Understanding Antihistamines: Benadryl and Allegra
Benadryl, with its active ingredient diphenhydramine, represents a first-generation antihistamine. This medication is known for causing drowsiness because it readily crosses the blood-brain barrier, affecting the central nervous system. Beyond its antihistamine action, diphenhydramine also possesses anticholinergic properties, which can lead to side effects such as dry mouth, blurred vision, and difficulty with urination. It works by blocking histamine-1 (H1) receptors, which are responsible for many allergy symptoms.
In contrast, Allegra, containing fexofenadine, is categorized as a second-generation antihistamine. A primary characteristic of fexofenadine is its non-drowsy nature because it does not easily cross the blood-brain barrier. Like Benadryl, Allegra also blocks H1 receptors to relieve allergy symptoms, but it does so with minimal anticholinergic effects. These distinct pharmacological profiles mean that while both drugs target histamine, their impact on the body, particularly concerning sedation, differs significantly.
Why Combining Antihistamines is Not Recommended
Taking Benadryl and Allegra together is not advised because both medications block histamine-1 (H1) receptors. These receptors trigger allergic reactions, meaning both drugs target the same biological pathway. Combining two H1 antihistamines does not enhance allergy relief, as one medication can saturate the receptors.
Instead, combining these medications amplifies their side effects. The sedative effects of Benadryl override any non-drowsy benefits from Allegra. This combination heightens the risk of adverse reactions without providing superior symptom control. Concurrent use is discouraged due to potential negative outcomes, not enhanced efficacy.
Potential Side Effects and Risks of Combination
The most notable and common side effect when combining Benadryl and Allegra is excessive drowsiness and sedation. Diphenhydramine, the active ingredient in Benadryl, is well-known for its sedating properties, which can be significantly amplified when taken with another antihistamine. This heightened sedation can severely impair alertness, making activities requiring concentration or quick reactions, such as driving or operating machinery, highly dangerous.
Beyond drowsiness, the combination can impair cognitive function and coordination. Individuals may experience difficulty concentrating, slowed reaction times, and reduced motor skills. Benadryl also contributes to anticholinergic effects, including dry mouth, blurred vision, urinary retention, and constipation. Combining medications with similar mechanisms increases the likelihood and severity of these effects.
Safer Approaches to Allergy Management
For effective and safe allergy management, consulting a healthcare professional is paramount. A doctor or pharmacist can provide personalized advice, especially before taking multiple medications or if allergy symptoms are severe or persistent. They can help determine the most appropriate single antihistamine or alternative treatment based on individual health needs and symptom profiles.
A safer strategy involves using one antihistamine at a time and assessing its effectiveness before considering other options. If oral antihistamines alone are insufficient, other safe and effective treatments are available, such as nasal corticosteroid sprays, antihistamine eye drops, or saline rinses. Implementing allergen avoidance strategies, like reducing exposure to triggers, also plays a significant role in managing symptoms. Always adhere strictly to the recommended dosage for any single medication to prevent adverse effects.